U.S. patent number 4,385,131 [Application Number 06/274,726] was granted by the patent office on 1983-05-24 for polyurethane foam resistant to smoldering combustion containing either urea or melamine.
This patent grant is currently assigned to Wm. T. Burnett & Co., Inc.. Invention is credited to Michael S. Buchanan, Roland N. Fracalossi, Walter V. V. Greenhouse.
United States Patent |
4,385,131 |
Fracalossi , et al. |
May 24, 1983 |
Polyurethane foam resistant to smoldering combustion containing
either urea or melamine
Abstract
Rebonded polyurethane foams having incorporated into the foam
urea and/or melamine are described. The rebonded foams have
excellent resistance to smoldering combustion and flaming
combustion. The rebonded foam is highly suitable, inter alia, for
cushioning and seating structures.
Inventors: |
Fracalossi; Roland N.
(Baltimore, MD), Greenhouse; Walter V. V. (Baltimore,
MD), Buchanan; Michael S. (Baltimore, MD) |
Assignee: |
Wm. T. Burnett & Co., Inc.
(Baltimore, MD)
|
Family
ID: |
23049368 |
Appl.
No.: |
06/274,726 |
Filed: |
June 18, 1981 |
Current U.S.
Class: |
521/55;
428/316.6; 428/317.9; 428/318.4; 428/319.1; 428/319.3; 521/128 |
Current CPC
Class: |
C08J
9/0028 (20130101); C08J 9/35 (20130101); C08J
2375/04 (20130101); Y10T 428/249987 (20150401); Y10T
428/24999 (20150401); Y10T 428/249981 (20150401); Y10T
428/249991 (20150401); Y10T 428/249986 (20150401) |
Current International
Class: |
C08J
9/35 (20060101); C08J 9/00 (20060101); C08G
018/14 () |
Field of
Search: |
;521/55,128
;428/316.6,318.4,319.1,319.3,317.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Welsh; Maurice J.
Attorney, Agent or Firm: Breiner; A. W.
Claims
It is claimed:
1. A flexible, cured polyurethane foam article which comprises
chips or particles of a polyurethane foam which is the reaction
product of a polyether or polyester polyol and a polyisocyanate
bonded together with a polyurethane foam binder, said polyurethane
foam binder being the product formed in a one-step reaction product
of a polyether or polyester polyol and a polyisocyanate, said cured
and bonded polyurethane foam article having substantially uniformly
incorporated therein a member of the group consisting of urea,
melamine, and mixtures thereof in an amount ranging from about 40
to 100 parts per 100 parts of polyurethane foam, said amount being
sufficient to provide resistance of the foam to smoldering
combustion.
2. The flexible, cured polyurethane foam article of claim 1 wherein
said urea or melamine is present in an amount of from about 50 to
75 parts per 100 parts of said polyurethane foam.
3. A flexible, cured polyurethane foam pad, said polyurethane foam
being the reaction product of a polyether or polyester polyol and a
polyisocyanate, said pad comprising chips or particles of said
polyurethane foam bonded with a polyurethane foam binder and having
substantially uniformly incorporated therein a member of the group
consisting of urea, melamine, and mixtures thereof in an amount of
from about 40 to 100 parts per 100 parts of foam chips or
particles, said amount being sufficient to provide resistance of
said polyurethane foam to smoldering combustion.
4. The polyurethane foam of claim 3 wherein said polyurethane foam
binder is present in an amount of from about 30 to 60 parts per 100
parts of chips or particles.
5. The polyurethane foam of claim 3 wherein said urea or melamine
is present in an amount of from about 50 to 75 parts per 100 parts
of chips or particles.
6. The method of making a flexible polyurethane foam pad having
resistance to smoldering combustion comprising (1) providing chips
or particles of a polyurethane foam which is the reaction product
of a polyether or polyester polyol and a polyisocyanate; (2) mixing
said polyurethane foam chips or particles with a member of the
group consisting of urea, melamine, and mixtures thereof to provide
a substantially uniform mix, said urea and melamine being
incorporated into said foam chips; (3) adding a liquid polyurethane
binder in an amount sufficient to bond said chips and urea and
melamine together; (4) compressing said mixture to provide a
selected density; and (5) curing said polyurethane binder to
provide a structurally unitary pad.
7. The method of claim 6 wherein said curing is accomplished by
applying low pressure steam to said compressed pad and thereafter
drying.
8. The process of claim 6 wherein said curing is performed by
adding water to the mixture of foam chips or particles and urea or
melamine, and thereafter passing warm air over said compressed
pad.
9. As an article of manufacture a cushioning material comprising a
rebonded polyurethane foam as defined in claim 3.
10. As an article of manufacture a cushioning material comprising a
resilient and flexible padding, a fabric layer, and positioned
between said padding and fabric layer a barrier layer comprising a
flexible, cured polyurethane foam pad as defined in claim 3.
11. The article of manufacture of claim 10 wherein the resilient
and flexible padding is a polyurethane foam padding.
12. The method of claim 6 wherein said polyurethane binder is used
in an amount of from about 30 to 60 parts per 100 parts of chips or
particles.
13. The method of claim 6 wherein said urea or melamine is present
in an amount of from about 50 to 75 parts per 100 parts of chips or
particles.
Description
This invention relates to polyurethane foams. More particularly,
this invention relates to rebonded polyurethane foams having
controlled density, strength, and resiliency characteristics which
are highly resistant to smoldering and flaming combustion.
The usage of polyurethane foams as a cushioning or padding material
has greatly increased in the last ten to twenty years, primarily
due to the excellent physical properties of polyurethane foams.
Polyurethane foams are available having soft and resilient
characteristics rendering them useful, for example, in pillows and
blankets. Other polyurethane foams have moderate load-bearing
characteristics and as a result are widely used, for example, as
seatings in furniture and as fillings for mattresses. Still other
polyurethane foam compositions are relatively firm and find
application in men's and women's apparel, packaging, thermal and
acoustical insulation, and carpet underlay. The versatility and
quality of the products that can be manufactured from polyurethane
foam are related to the advances that have been made in the
chemistry of polyurethane raw materials and in the technology that
has evolved in the formulation and processing of materials into
satisfactory and needed products.
While the marketplace for polyurethane foams has witnessed
innovations and improvements which have led to greatly expanded
usage of polyurethane foams, there has been increasing concern that
more needs to be done to reduce the fire potential of polyurethane
foams. This concern with respect to fire is partly related to the
increased effort which has been expended in recent years to reduce
the number of injuries and fatalities to people that are caused by
fires whatever the reason and source. Emphasis has been placed on a
nuamber of factors that directly influence the magnitude of fire
problems, both in terms of human suffering and physical damage or
loss of property. For example, educational programs in fire
prevention are conducted widely; fire alert and fire protection
systems have been improved. As a corollary to this concern, in
recent years federal, state, and local regulations have been
established intended to protect life and property from fire. These
regulations often impose rigorous requirements in the
specifications set for materials and products used by the consumer
so as to make the materials and products safer for use. Many of
these requirements take the form of test procedures designed to
assess the fire potential of a particular material. In most cases
the test procedure is small in scale, but some tests approach the
dimension of a full-scale evaluation. In either case there is an
effort to determine the fire potential of a material under
controlled conditions.
The prior art of polyurethane foams establishes considerable
activity with regard to reducing the fire potential of polyurethane
foams. The use by the foam industry of chemical substances that are
described as flame-retardant or combustibility modifiers has
increased substantially. While considerable progress has been made
in a number of areas of foam application and polyurethane foams
have been produced that show improved resistance to an open flame
or spark, there has been insignificant progress in the effort to
prevent fires started under conditions of smoldering combustion.
For example, an upholstered chair or sofa in the home or office can
be very susceptible to ignition from a lighted cigarette dropped
upon it. There have been upholstery fabric constructions in use
over polyurethane seating assemblies that give rise to uncontrolled
smoldering of the fabric and the foam, which leads to ignition and
destruction of the furniture. Fabrics of the above type have been
sorted out by tests and described as Class II fabrics by the
Upholstered Furniture Action Council (UFAC), an industrial group
that represents a large number of furniture manufacturers in the
United States. Class II fabrics have been popular because they
provide the fabric manufacturer with greater versatility in design,
structure, and weight of fabric--features that are obviously more
attractive to the homeowner. Other fabrics have been designated as
Class I by UFAC. These Class I fabrics can be used over
polyurethane foam seating assemblies without causing smoldering
combustion in the presence of a lighted cigarette. Class I fabrics
are of limited construction and, while obviously safer to use,
offer less in fabric selection and features.
It is a primary object of this invention, therefore, to produce
polyurethane foams that can be used in upholstered furniture with
either Class I or Class II fabrics as designated by the UFAC
without causing ignition of the foam cushioning or furniture using
the foam cushioning by lighted cigarettes and the like.
It is another object of this invention to provide polyurethane foam
that, in addition to providing cushion assemblies which are
resistant to cigarette ignition, meets ignition tests which are
widely used to determine a material's relative resistance to an
open flame, such as Federal Motor Vehicle Safety Standard No. 302
which has application to all materials used in the interiors of
automobiles; and Federal Aviation Administration Regulation No.
25.853 which regulates the flammability characteristic of materials
used in the interior of aircraft.
It is another object of this invention to produce polyurethane foam
having properties that are functional and desirable in comfort
cushioning, while at the same time providing significantly improved
safety features in the way of increased resistance to both
smoldering and flaming combustion.
It is still another object of this invention to provide a process
for the production of polyurethane foam compositions having the
aforesaid resistance to smoldering and flaming combustion.
These and other objects of this invention will be made fully
apparent from the following general description and the detailed
description in the preferred embodiments.
The aforesaid objects of this invention are realized by
incorporating urea or melamine or a mixture of urea and melamine
(hereinafter, at times, "the smoldering retardant additive") into
cured polyurethane foam materials in select amounts. In a
particularly preferred embodiment the smolder retardant additive is
admixed with shredded or ground polyurethane foam, and the
admixture adhesively bonded into dimensionally stable molded
configurations. The polyurethane foam obtained is resistant to
smoldering and flaming combustion when used alone in foam products
or in foam/fabric assemblies. Additionally, the physical
characteristics such as density, strength, and resiliency can be
controlled, permitting use of the foam materials in a variey of
applications including seat cushions; padding used in furniture;
mattresses and bedding construction; interiors of automobiles,
truck, and buses; marine and aircraft seating and interior
assemblies; and cushioning or packaging material designed to
provide comfort or support either to people or to other materials
of construction. Further, cured polyurethane foam is available as
scrap material from other operations utilizing polyurethane foam
and, thus, is a relatively inexpensive raw material. Heretofore,
however, because of appearance and physical characteristics, bonded
or rebonded polyurethane foam was used primarily in the form of
underlayment for carpet and rugs where the appearance of the foam
was not critical. According to the present invention, however,
polyurethane foams can be provided which are resistant to flaming
and smoldering combustion, and have the essential physical
characteristics which permit use of the foams in applications where
conventional rebonded materials have not been capable of use, and
can be used in applications which heretofore required virgin
polyurethane foam.
The polyurethane foam suitable for use according to the present
invention are foams derived from hydroxyl terminated polyester or
polyether polyols reacted with organic diisocyanates in the
presence of suitable catalysts, surfactants, and blowing agents.
Most any polyurethane foam which can be shredded into discrete
particles or chips can be adhesively bonded in the presence of urea
and/or melamine. Additionally, although the urea and melamine
provide resistance to flaming combustion as well as to smoldering
combustion, it has been found that flame retardant agents, in
addition to the urea and melamine, can be incorporated into the
foam during the initial manufacture of the foam or during the
bonding process. In this manner rebonded polyurethane foam products
can be made that have even greater resistance to flaming
combustion. However, the presence of these conventional flame
retardant agents did not show any significant improvement in the
product's resistance to smoldering combustion.
Flame retarding agents that can be used in addition to the urea and
melamine are those known in the art for polyurethane foams and
include organic and inorganic compounds that contain varying
percentages of chlorine and/or bromine, phosphorous, combinations
of halogen and phosphorous, and substances such as antimony oxide,
hydrated alumina, and compounds containing boron. These materals
can be used in the solid or liquid form. If used as solids, they
can be admixed with the foam chips or shredded foam along with the
urea and/or melamine. If used as liquids, they can be incorporated
along with the binding adhesive or can be sprayed onto the chipped
or shredded polyurethane foam prior to the addition of the
adhesive.
Examples 1-4 will establish the effectiveness of urea and melamine
in providing smoldering and flame-resistant rebonded polyurethane
foam. Example 1 demonstrates the improvement in accordance with
this invention utilizing urea. Example 2 demonstrates the
improvement in accordance with this invention utilizing melamine.
Examples 3 and 4 demonstrate the lack of smoldering and
flame-retardant characteristics in rebonded polyurethane foams in
the absence of urea and/or melamine.
EXAMPLE 1
Flexible polyether polyurethane foam made by the one-shot process
to produce conventional cushioning material was shredded on
commercially available grinding equipment to yield foam chips
having particle sizes typically in the range of one-fourth to
one-half inch in diameter. The foam did not contain flame-retarding
agents. The foam chips were tumbled in a container equipped with
rotating mixing paddles and while tumbling, to each 100 parts by
weight of the foam chips, 56 parts by weight of fine particle sized
urea is added. The urea was passed carefully through a screening
device in order to achieve good distribution as it entered the
mixer and contacted the foam chips as they tumbled inside. Tumbling
was continued until a good mix was obtained. Examination of the
mixture at this stage revealed significant penetration of the urea
into the cellular structure of the foam. Some of the urea could
also be seen at the surface of the foam chips. While still
tumbling, 44 parts by weight of liquid polyurethane binder was
added in a uniform manner into the mixture of chips and urea, and
the final blend was further tumbled until all liquid binder was
well distributed and fully absorbed by the foam. The polyurethane
binder utilized is the reaction product of a polyether polyol
having a molecular weight in the range of about 3,000 to 6,500 with
toluene diisocyanate in the presence of a catalyst, i.e., stannous
octoate, a surfactant component, i.e., organo-silicone compounds, a
tertiary amine catalyst, i.e., N-ethyl morpholine, and sufficient
cellosolve acetate solvent to provide a sprayable mixture. The
blended material was then placed into a mold and compressed so as
to obtain a density of 3.3 pounds per cubic foot. The blend was
exposed to live steam for five minutes at low-pressure (maximum 10
psig) in order to bond and cure the blend to the specific density
after which the compressed pad of rebonded polyurethane foam was
dried in a hot air oven. The rebonded polyurethane foam pad had
good strength and resiliency, and the particles of urea were
tightly bound within the foam matrix structure. The pad was flexed
in a compression apparatus for 100,000 cycles, and it was
determined that the pad retained its weight and structural
integrity after the flexing. The pad was tested for resistance to
ignition from a lighted cigarette in accordance with UFAC
procedures described in the UFAC bulletin "Polyurethane Foam Test
Method." The cover fabric used was standard Class II fabric as
described by UFAC bulletin "Fabric Classification Test Method." The
rebonded polyurethane foam prepared according to this example
successfully met all of the conditions of the test. There was no
ignition of the assembly and the vertical char produced was
three-quarters of an inch and less.
In addition to having good resistance to smoldering and
flammability combustion, the foam pad was tested for load-bearing
characteristics in accordance with ASTM test method D-1564. The pad
gave a 25 percent ILD of 35 pounds, and a 65 percent ILD of 125
pounds. The ratio of the load at 65 percent divided by the load at
25 percent, recognized in the furniture, mattress, and automotive
seating industry as a support factor which is desired to be at
least 2.0 and preferably greater than 2.0; is calculated to be 3.57
which is a significant improvement and establishes the
marketability of the rebonded product in such application. The pad
was tested and found to meet the flammability of the Federal
Aviation Administration Regulation No. 25.853 which applies to the
compartment interiors of aircraft. The requirement under paragraph
(b) of this federal standard is that the part used, for example
seat cushions, when tested as prescribed; not have an average burn
length exceeding eight inches, or an average flame time after
removal of the flame source not to exceed 15 seconds, or have
drippings from the test specimen continue to flame for more than an
average of five seconds after falling. The pad prepared by this
Example 1 under this test gave an average burn length of two to
three inches, an average flame time of zero to three seconds, and
an average flaming dripping time of zero to two seconds.
EXAMPLE 2
Example 1 was repeated in all respects except that melamine
replaced the urea in the following proportion of components. To 100
parts by weight of the foam chips that were used in Example 1 was
added about 67 parts by weight of melamine. The weight of liquid
polyurethane binder used was 44 parts. The pad that was made had a
density of 3.60 pounds per cubic foot, a 25 percent ILD of 33, a 65
percent ILD of 120, giving a support factor of 3.64. The results of
the UFAC cigarette ignition test demonstrated that no ignition of
the filling/fabric assembly occurred, and the vertical char
produced was one and one-fourth inches and less. This pad met the
requirements of FAA Regulation No. 25.853 demonstrating an average
burn length of three to four inches, an average flame time of zero
to seven seconds, and an average flaming dripping time of zero to
three seconds.
EXAMPLE 3
Example 1 was repeated in all respects except that in this instance
no urea or melamine was added to the foam chips or particles. The
blended material prepared as described in Example 1 was placed into
a mold and compressed so as to obtain a density of approximately
2.5 pounds per cubic foot. After being exposed to live steam and
dried, as described in Example 1, the rebonded polyurethane foam
was found to have excellent resiliency and strength well suited for
use as a seating material.
For comparison purposes another pad designated as pad Example 3a
was cut from a block of regularly produced (not rebonded)
conventional flexible polyether polyurethane foam, which like the
pad of this Example 3 did not contain any flame-retarding agent.
Both pads, Example 3 and Example 3a, were then tested for
resistance to ignition from a lighted cigarette by the procedure
described in the UFAC bulletin noted in Example 1. The cover fabric
which was over the pads was a standard Class II fabric as defined
in the UFAC bulletin described in Example 1. Both pads Example 3
and Example 3a failed the test criteria due to ignition of the
filling/padding materials and extensive propagation of smoldering
combustion.
EXAMPLE 4
To further demonstrate the effectiveness of the addition of urea or
melamine as an additive to the foam composition, for purposes of
comparison, to 100 parts by weight of the foam chips that were used
in Example 1 there were added 36 parts hydrated alumina, 25 parts
ammonium polyphosphate, 24 parts decabromodiphenyl oxide, and 22
parts tris(chloropropyl)phosphate. The weight of liquid
polyurethane binder used in bonding the foam particles was 51 parts
per 100 parts of the foam chips. The pad formed in accordance with
the process of Example 1 had a density of 3.35 pounds per cubic
foot, a 25 percent ILD of 30 pounds, a 65 percent ILD of 105
pounds, giving a support factor of 3.5. The pad as thus produced
was found to meet the flammability requirements of Federal Motor
Vehicle Safety Standard No. 302 wherein one-half inch specimens
were unable to maintain a burning rate and extinguished themselves
within a short time after ignition. However, the pad of this
example failed the test criteria of the UFAC cigarette resistance
test with Class II fabric due to ignition of the filling/padding
material as well as extensive propagation of smoldering
combustion.
In addition to providing polyurethane foams which are excellently
suitable for use as cushioning materials, either alone or in
combination with fabric materials, it has been found that the
rebonded polyurethane foam containing the urea and/or melamine as
described hereinbefore can be used in the form of a barrier layer
which is wrapped around or covers in part a seat or cushion made
from conventional polyurethane foam. This particular assembly or
structure not only preserves the support and comfort of the primary
polyurethane foam cushion, but the barrier layer provides the
resistance to smoldering combustion that cannot be obtained with
conventional cushioning in contact with Class II fabrics. By way of
explanation, it is to be understood that the barrier layer, as
above described, lies positioned between the upholstery fabric and
the foam cushion material. The ability to use the rebonded foam of
this invention as a barrier layer makes it possible for a wide
variety (from soft to extra-firm, for example, or from lower to
higher density) polyurethane foams to have application as seating
or cushioning in combination with a broad selection of Class II
materials. Where economics plays a sufficient role, this ability
will permit savings in the cost of the seating which might
otherwise require special materials, formulations, or
post-treatment to ensure compliance with safety standards. Example
5, hereinafter following, establishes how rebonded polyurethane
foam can be made into a barrier material that can be interposed in
the form of a sheet or liner between conventional, non-flame
retardant foam cushioning and Class II fabrics to shield the
assembly from cigarette ignition.
EXAMPLE 5
To 100 parts by weight of the foam chips that were described in
Example 1 was added 64 parts by weight of urea and about 55 parts
by weight of liquid polyurethane binder also as described in
Example 1. The blended material was placed in a mold and compressed
so as to obtain a density of approximately 4.0 pounds per cubic
foot. The blend was then steam-cured and dried as described in
Example 1. The rebonded polyurethane barrier material obtained
after the steam-curing and drying had excellent strength and
resiliency, and the particles of urea were tightly bound within the
foam matrix structure. A sheet of this material approximately 3/8
of an inch in thickness was tested in accordance with the UFAC
bulletin "Barrier Test Method." The foam obtained corresponded in
properties to Product Code 2715 as given in the UFAC bulletin.
Results of the lighted cigarette test showed no ignition of the
assembly, and the vertical char was limited to about 3/8 of an inch
or less.
An additional feature in accordance with the present invention is
that it is possible to capitalize on the availability of scrap
polyether and polyester urethane foams to meet a characteristic
heretofore unavailable with polyurethane foams; that is, it is
possible to bond or rebond foams having the desirable
characteristics of both polyester foams and polyether foams. For
example, it is possible to utilize foam chips of less resilient
polyester polyurethane foams in combination with foam chips of the
normally more resilient polyether urethane foams. It is also
possible to achieve even more specific properties in the rebonded
product by blending together, in suitable and different
proportions, foam chips of both polyester and polyether urethane
foams which, in addition to having the combined features of
polyester and polyether foams, have substantial resistance to
smoldering combustion as well as flaming combustion. This type of
foam is illustrated in the following example.
EXAMPLE 6
The foam chips of this example were produced by shredding polyester
polyurethane foam to yield chips whose dimensions were typically
one-fourth inch to three-fourths inch in length and/or width, and
in the range of 0.030 inches to 0.250 inches in thickness. The
thickness dimensions given arise from the fact that the polyester
foam stock was in the form of thin sheets of material that had been
peeled on commercial cutting equipment from cylindrical blocks of
foam material. Polyether foam chips having the dimensions as
described in Example 1 were admixed with the polyester chips at the
ratio of approximately 50:50. To 100 parts by weight of the mixture
of polyester and polyether foam were added 55 parts by weight of
urea and 37 parts by weight of liquid polyurethane binder. The
materials were processed as described in Example 1. The blended
material was placed in a mold and compressed so as to obtain a
density of approximately 3.5 pounds per cubic foot. The blend was
then steam-cured and dried as in Example 1. The rebonded
polyurethane foam pad had the desirable characteristics of a
polyester foam pad and, also, the desirable characteristics of a
polyether foam pad. The foam pad satisfied all of the criteria of
the UFAC cigarette ignition test as described in Example 1, and
further satisfied the requirements of the FAA Regulation No.
25.853.
In the aforesaid examples and in accordance with the present
invention, the smoldering retardant additive can be present at from
about 40 to 100 parts per 100 parts of polyurethane foam chips.
Preferably the smoldering retardant additive will be present at
from about 50 to 75 parts per 100 parts of polyurethane foam chips.
It has been observed that not all Class II fabrics are affected
equally when used in combination with polyurethane foam and exposed
to smoldering combustion. Therefore, it may be necessary to use
more or less smoldering retardant additive for a particular
application.
Further, although both urea and melamine provide resistance to
smoldering and flaming combustion, at times, depending upon the end
application of the foam, one material can be preferred over
another. For example, melamine is not water soluble. Accordingly,
if the end product is a product which is to be subjected to water
washing, melamine is the preferred smolder retardant additive. For
certain other applications, urea would be a logical choice.
The liquid polyurethane binder as employed herein and as stated in
the examples which can be any of the known urethane formulations
that can be cured to provide a flexible cellular material is
present in an amount sufficient to provide good bonding, and
normally will be used in an amount of 30 to 60 parts per 100 parts
of foam chips. The binder can be prepared from the required
components and used immediately, or it can be stored in closed
containers for later use. It is normally required that the binder
be thinned with a suitable solvent, such as cellosolve acetate, so
that it can be sprayed with equipment that employs either the
airless or air-type principle.
While the examples as set forth hereinbefore illustrate the use of
live steam at low pressure to expand and cure the binder in
combination with the compressed foam chips, other methods can also
be utilized. One such method comprises adding water to the foam
chips and mixing thoroughly prior to the addition of the liquid
polyurethane binder. Thereafter, after all of the various
components required for the composition have been added and the pad
compressed to the desired density, warm air is then passed through
the pad to expand, cure, and dry the rebonded polyurethane
material.
As previously stated, the present invention permits the use of
virtually any cured polyurethane foam in the preparation of the
improved polyurethane foams having resistance to both smoldering
and flaming combustion. These foams, as known to one skilled in the
art, can be based on polyester or polyether polyols reacted with
the various polyisocyanates such as toluene diisocyanate. As
previously mentioned, the present invention is imminently suitable
for use with scrap polyurethane foam materials such as scrap
material obtained in other polyurethane foam operations, including
the fabrication of thin sheets of polyurethane foam derived from
peeling round blocks of polyurethane foam. Further, although the
examples, as set forth hereinabove, are primarily concerned with
rebonded, cured polyurethane foam which is the highly preferred
embodiment, it is possible to impregnate cured virgin polyurethane
foam with urea and/or melamine as, for example, by forming a
solution of urea in water and applying it uniformly to blocks or
pads of polyurethane foam; or forming a solvent solution or
dispersion of melamine and applying the solvent solution or
dispersion to blocks or pads of polyurethane foam. Provided that
the urea and/or melamine is uniformly impregnated in the amounts
stated hereinbefore, the smoldering combustion characteristics of
the foam will be greatly enhanced.
The effect of the urea and/or melamine on the cured polyurethane
foam is particularly surprising in that conventional flame
retardants such as the halides, phosphorous compounds, and the
boron-containing materials commonly used for this purpose with
other materials such as cotton have little or no effect on the
smoldering characteristics of polyurethane foam.
While the cured polyurethane foam of this invention is well suited
for use in cushioning for seating and mattresses, it has other uses
in various resilient products where such applications require more
smolder-resistant and flame-resistant foam materials. These
applications include textiles such as wearing apparel and blankets;
thermal and acoustical insulation for home, industry, and
transportation; packaging for military and industrial hardware; as
well as carpet underlayment; air filters; athletic equipment, toys
and novelties--as examples only.
Various modifications to the invention as above described will be
apparent to those skilled in the art.
* * * * *